What size expansion vessel do I need for a 15 Litre water heater?

What size expansion vessel do I need for a 15 Litre water heater?

2 Litre
Potable Expansion Vessel Sizing Guide

Cylinder Size Expansion Vessel Size
5-15 Litres 2 Litre
30 Litres 5 Litre
50-80 Litres 8 Litre
90-125 Litres 12 Litre

Can I fit my own expansion vessel?

No , your ok to do it as long as you are not tampering with a gas appliance, or gas supply. Get a large capacity expansion vessel (12lt or more) , tee in to return near the boiler.

Can you over size an expansion vessel?

It’s no difference to fitting an enlarged header tank, as long as it takes up the expansion of the system water, the system will operate correctly.

Do I need a bigger expansion vessel?

As we all know, when water is heated it expands and wants to take up more volume. As the system is basically a closed loop, consisting of the boiler, pipework and radiators, it is necessary to provide some space for the water to expand into. This is why the expansion vessel is required.

Should an expansion vessel have water in it?

There should be water in the water side of the expansion vessel. It is actually preferable that all air is removed from the water side.

How much water does an expansion vessel hold?

Between 1 bar and 2.7 bar, the expansion vessel can hold an additional 6.2 litres, which is the so-called expansion volume. This is more than sufficient for the 3 litres of actual expansion water.

What is a Zilmet expansion tank?

Zilmet pressure vessels are made up of a replaceable butyl diaphragm mounted in a mild steel shell eliminates any contact between the water and the steel shell of the vessel. All units up to and including 25 litre sizes are suitable for a working pressure of 8 bar and the larger vessels 10 bar (except 1000LV).

How big should my expansion vessel be?

Vessels are sized according to the volume of the system and the maximum temperature that the system generates, we also must consider the static head above the vessel….

System Volume (L) Expansion Vessel Size (L) Boiler Output (kW)
3000 250 250
5000 400 417
7500 600 625
10000 800 833

Can you Oversize an expansion tank?

In fact, if unsure that your expansion tank will be able to safely accommodate your system, it is common practice to choose an expansion tank that is one size larger than the required size. As a general rule of thumb with expansion tanks, it is better to oversize than to undersize.

How do I know if my expansion vessel is faulty?

If water comes out of the valve you have a definite expansion vessel fault. In this case the vessel has definitely failed and must be replaced. If no water comes out but no air either, you have an expansion vessel fault but the diaphragm may still be intact and it may be possible to re-pressurise.

What pressure should my expansion vessel be?

Some important things to consider is the air pressure inside the expansion vessel. It rarely needs to be anything more than 1.5 bar in most domestic properties. Anything more and the water may not expand into the air at the required time and could risk the high pressure relief valve opening or worse.

What happens if expansion vessel is too small?

When water is heated, it can expand to between four and nine per cent of its original volume. This means that an expansion vessel that is too small may not be able to perform its job sufficiently and won’t take enough water out of the system to bring the pressure back down.